Wine Words: Rootstock

Rootstock is a wine word that many readers probably
have heard mentioned with regard to viticulture and the growing of wine grapes. Today most vines are planted on rootstocks. This means that they are not planted on their own roots; rather the vine is grafted onto the root of a different vine species.

Almost all of the grape varieties used to make wine
belong to the Vitis Vinifera species. In contrast most rootstocks are American
hybrids derived from non-Vinifera vine species. Typically hybrids are from
Vitis Riparia, Vitis Rupestris and Vitis Berlandieri.

Why use rootstocks?

The use of rootstocks dates back to 1800s when most
of the world’s vineyards were attacked by a root louse called Phylloxera.
Phylloxera basically attacks and kills vines. After considerable effort
to find a solution to Phylloxera, it was discovered that non-Vinifera vine
species seemed resistant to attack. The problem is that the wine made from
non–Vinifera vines does not taste very nice.

Viticulturists and scientists then discovered that
by grafting the Vinifera grape vine onto the root on an American hybrid it
resisted Phylloxera attack. Moreover they found that the Vinifera variety
maintained its original taste and aroma characteristics.

Ungrafted vines

The threat of an outbreak of Phylloxera continues to
plague the vine growing world. Therefore most vines continue to be
planted on rootstocks. That said, there are pockets of vineyard areas which have
not been affected, either because the soil is inhospitable to the lifecycle of
the Phylloxera louse, or, for some reason Phylloxera never made it to the
vineyard in question.

Most of South Australia and New South Wales in
Australia, Chile, and the island of Santorini off Greece as well as a few
isolated vineyards throughout the world are known to be Phylloxera free.

In such regions, growers can continue to plant the
vine on its own roots. However, rootstock research and development has evolved
significantly and become very sophisticated. Apart from using a
rootstock to combat Phylloxera, growers choose rootstocks to manage all sorts
of other viticultural issues such as vine or soil vigor, soil acidity or
alkalinity, drought, dampness, soil salinity, etc.